1. Field of the Invention
The present invention relates to a portable transmitter, which is advantageously used as a transmitter in a keyless-entry system for an automobile and in a keyless-starter system.
2. Description of Related Art
An example of this kind of transmitter is disclosed in JP-A-2001-140513. A transmitter similar to the disclosed transmitter is made by the inventors of this application as a prototype, which is briefly shown in FIG. 11. A printed circuit board 31 on which tact switches 32 are mounted, knobs 170 for pushing the tact switches 32 and all other components are contained in a case composed of a front case 110 and a rear case 120. The front case 110 is connected to the rear case 120 by inserting projections 110a formed on the front case 110 into depressions 120a formed on the rear case 120. A button-type battery 20 for supplying power to the electronic components is also contained in the case. The printed circuit board 31 is covered with a water-protecting cover 18a, and a seal member 18b is disposed between the front case 110 and the rear case 120 to keep the case water-tight.
Front openings 110f are formed in the front case 110, and the knobs 170 are exposed from the openings 110f. Function displays 170b, 170c, 170d, which show figures or characters corresponding to devices to be operated by pushing the respective knobs, are formed by molding colored resin materials on the knobs 170. If the function displays were printed on the knobs 170, they would be erased by being frequently touched. In this prototype, the function displays 170b, 170c, 170d are formed by molding so that they are not erased in a long term use of the transmitter.
It is necessary to provide a certain space or clearance between the knob 170 and the front opening 110f in inserting the knob 170 into the opening 110f. It is highly possible that clearances at four sides of the openings 110f are not equally formed, damaging an ornamental design of the transmitter. When changes in the function displays are required, dies for molding the respective function displays have to be newly prepared. This makes production costs high. Further, it may be required to increase a repulsive force of the knob 170 against a pushing force in order to avoid inadvertently pushing the knob. It is difficult to increase the repulsive force in the prototype structure because the repulsive force is exclusively determined by the repulsive force of the tact switch 32 itself.